1. Field of the Invention
The invention relates to a pump for pumping fluid, and in particular, to a piezoelectric axial pump suitable for use as a heart pump, or the like.
2. Description of the Related Art
The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge.
Currently, tens of thousands of patients suffer from heart failure worldwide. For example, a patient in the U.S. has suffered with heart failure for most of her adult life. Diagnosed at age 25, doctors attribute her heart failure to a hereditary condition. Her father shared the same disease and died at age 32 more than 20 years ago. Development of a heart assist device that can be implanted into the body and help the heart to pump the blood is necessary in aiding patients with such conditions.
Conventionally heart pumps are implemented in the form of electromagnetic pumps. However, pumps of this form suffer from a number of problems, such as the fact that the apparatus is relatively heavy in weight, has a large size and can be affected by external magnetic fields. Furthermore, the operation of the pump can lead to the generation of vortices in the blood.
It is therefore necessary to develop a heart pump that can assist the heart to pump the blood to the whole body at heart failure. In particular, it is desirable that the pump is small, light-weight, has a low power consumption, does not generate vortices in the pumped blood and is minimally affected by the external factors, such as magnetic fields.
An example of a piezoelectric rotator is shown in U.S. Pat. No. 6,388,364. In this example, the rotator uses piezoelectric members that operate to expand and contract in a predetermine manner to cause rotation of a ring. However, the performance of such configurations is limited. In particular, the piezoelectric members extend across the ring, thereby restricting the usefulness of this form of motor in fluid pumping applications. Furthermore, rotators of this form tend to generate rotational torques, and are therefore generally unsuitable for fluid pumping applications.